Aminodextran (often abbreviated “Amdex”) is a high molecular weight polymer comprising a mostly linear chain of glucose residues with chemically introduced pendant amino groups. These amino groups can be activated and conjugated to a variety of proteins. Because of its low nonspecific background binding to cells, its high water solubility, and its ability to vary its amine content by adjustment of reaction conditions, the aminodextran polymer has long been useful as a component of amplified labeled conjugates with proteins, such as streptavidin or monoclonal antibodies. The preferred label in such conjugates is a fluorescent label. Fluorescent proteins, such as phycoerythrin, have also been attached in large numbers to the aminodextran polymer to produce reagents with high specificity and enhanced fluorescent intensity. Numerous such particles have been described as reagents for use in cell labeling for flow cytometry uses. See, for example, the inventor's prior publications including U.S. Pat. Nos. 5,891,741; 5,994,089 and 6,387,622, among others, as well as O. Siiman et al, 1999 Bioconj. Chem., 10(6):1090–1106.
Other uses of aminodextran and aminodextran-protein conjugates are described in, e.g., U.S. Pat. No. 5,424,297 which refers to adenosine dextran conjugates for treating hypertension; U.S. Pat. No. 5,543,332 which refers to other water-soluble conjugates and reagents; and U.S. Pat. No. 6,287,568, which describes immunogenic dextran-protein conjugates for use as vaccines and adjuvants; and U.S. Pat. No. 6,207,385 describes nucleic acids bound to dextran carrier macromolecules. T. M. Hansen, 2003 IVD Technol., pp.35–40 describes fluorescent dextran conjugates for use in quantitative assays. International Patent Application No. WO00/07019 (10 Feb. 2000) describes methods for preparing water soluble cross linked conjugates.
U.S. Pat. No. 5,627,078, describes multivalent dextran reagents for use in precipitation tests. This multivalent reagent employs dextran with a MW of 10 kDa up to the solubility limit of about 2000 kDa, and preferably employs MW of 20 to 500 kDa. These reagents have a ratio of dextran:bound molecules of about 1:5 to 1:50. See, also, C. W. Cairo et al, 2002 J. Am. Chem. Soc. 123, 1615–19. These documents and those cited above are incorporated by reference to provide information on presently known aminodextrans and uses of same in aminodextran conjugates and other forms.
However, problems associated with the use of aminodextran conjugates include inconsistent yields and amplification that vary between preparation lots of the conjugates, and even from chromatographic fraction to fraction within a lot. The use of such inconsistent lots of the aminodextran polymer has resulted in less efficient labeling than desirable for diagnostic procedures involving cell labeling.
There thus remains a need in the art for methods and compositions that overcome the deficiencies of currently employed aminodextran conjugates, while retaining their useful qualities as cell labeling reagents.